Electron discharge circuit



Nov. 21, 1944.

W. W MOE ELECTRON DISCHARGE CIRCUIT Filed April 24, 1942' lnv enborz William W. Moe,

- His Attorney.

I j, TITheieet es of my ention whi h I Patented Nov. 21, 1944 William W. Moe, ;,Stratford, :Conm, .assignor to General Electric Company, a iconporation New York v Application April 24, 1942, Serial No. 440,313

4 Claims.

My invention relates to electron discharge circuits, and'more particularly to oscillating'circuits incorporating electron discharge devices.

Certain types of oscillating circuits, in'which electron discharge devices are used as the'driving elements and n which the operating bias for I suchdevices is produced'by their own oscillation, tend to oscillate. intermittently. That is,

the oscillating circuit operates at its normal "fre- 1 quency for a short period of time during which an excessive operating bias for the electron dis' charge device is built up, such bias being of sufficient' magnitude to stop operation of the oscillaltor; Afterthe operation at normal frequency stops, the electron discharge device beingjsimultaneously stopped from producing its own operating bias, the excessive operating bias is gradually reduced to a point at which normal operatioh can be resumed. Such intermittent operation of anoscillating circuit is commonly terrne blocked oscillation. e 7

Such blocked oscillation is generally encountered in oscillators in which the operating bias device I2.

the device I2 is maintained intermediate the potentials of theends of the tuned circuit I0 by asecond tunedcircuit I6, which is coupled in suitable manner, as by induction, to the tuned circuit In and which is connected between the is produced by grid rectification of the oscilla- I tions across a resistance in circuit between grid and cathode oi the electron discharge device, the

resistance being of toohigh a value. However, when certain oscillating circuits are operated at ultra high frequencies, of the order of from 500 to 3,000 megacycles and higher, such blocked oscillations are produced even though the resistance across which the operating bias is produced is of relatively small value.

Itis anobiect of my invention to pr vi e a new andimpro'v d cillat ng c cuit. in whis 'it e tendency t Qroduee such b oeked'osc ations is minimizede ion to produce s ch an o cilla or eireui-tin whishithe tende ey to produce excessWeop p tin bias po ent als is minimized- Z believe It is a corolla y obi'ect .1 my incontrol electrode IgI and cathode 15 through a condenser". v I "Operating current is supplied to the discharge device I 2 from a sourceof potential (not shown) whose negative terminal is connected to ground and whose positive terminal is connected through V a large inductance 2| and through a small inductance I8 to the anode I4 of the device I2. Bias-potential 'for the control electrode II is developed across a suitable-resistance I 9 connected between ground and thatend of the tuned cir-- cuit I6 opposite to the control electrode I I.

It may be found that the oscillating circuit; with an constants adjusted to desired values,

tends to produce blocked oscillations described previously. This maybe true at ultra high frequencies, even though the resistance I9 is of relatively small value. In' such cases, a condenser 20 is connected from a point between the inductances 2I and I8 to a point between the resistance I-9 -and the tunedcircuit IS. The inductance I8 is just sufiiciently large to present a high reaotance to' current of thefrequency to which the circuits I 0 and I6 are tunedjwhile -presenting substantially no reactance 'tocurrent of the frequen'cy at which the oscillating circuit tends to block. The inductance "2| is of much higher value, and presents a large reactance to current ofthe frequency at which the oscillating circuit tends to block. The condenser 20 is of suflicient'capacity to present small reactance to current of the frequency at which the osci1- lating circuit tends-to block.

In operation, with the discharge device I2 producing oscillations in the tuned circuits I0 and o benpvel are set. forth. with particularity in thcapn nded. claims- ,My nvention itse i,both

egether with furthe object a d'advantages thereof may best be unde eed b r ferencetto he .feollowi gdescr ntion et -k n in nnection as to its 'oreani at on and manner of operation; 4

wi h -theace mpanyingudrawins i which Fi repr sentsone mbodiment of my inve tion, andl igQZ represents-a odifi ation thereof, e

In' Fig. 1; one end of a tuned circuit "Ill isf conneet dto the grid l o an electron d schar e devi e 2, Who e eathode I5 is grounded- (The other endoi the tuned circuit In i connected through condenser is to. the anode up: the

I 6, whenever the oscillating circuit tends to block, the anode current of the device I2 tends to become smaller and, though the condenser 2i], consequently reduces the excessive bias potential developed across resistance I9, This operation takes place in the followingmanner. When, for

any reason, the bias potential developed across the resistance I9 tends to become excessively large, thereby making the control electrode I If so negative in potential as to reduce the dis? charge current flowing through the device I2','the

current through the large inductance 2|- is de'- creased, and the potential drop thereacrosstcorrespondingly reduced. The potentialof 'the'pcint' The potentialflof the cathode l 5 of resistance l9, such reductionof this bias poten- Since the blocking action the blocking action on the control electrode of the oscillator in such phase as substantially to eliminate the blocking action. In this figure the electron discharge device I2 is similar to the device 12 in Fig. l, and like reference numerals are applied to like parts thereof.

A tuned frequency determining circuit ineluding an inductance 30, and a condenser 3! connected in parallel thereto, is connected at one end to the anode M and at the other end through a condenser 32 to the control electrode tial through the coupling of the resistance is effective to minimize, and in fact substantially eliminate, such blocking action.

The condenser 11, which is connected between one end of the tuned circuit [6 and the cathode l5 to provide a low impedance path therebetween at the frequency of oscillations, must have a low reactance at such frequency. Howeventhis condenser ll must have substantial reactance at the frequencyof the blocking action which it is desired to suppress. Otherwise, voltage of the frequency of the blocking action appearing across the inductance 2| could not be impressed across the resistance l9 through condenser 20.

Viewed in another fashion, the action of the inductance 2| and-condenser 20 in preventing such blocking action is to produce degenerative feedback from theanode circuit to the control electrode circuitofthe oscillator, such feedback being effective only at the frequency of the blocking action and being sufficient in magni That is,

tude to prevent such blocking action. the inductance l8, terminated by the condensers 20 and IT, forms a low pass filter which prew.

vents transmission. of the high frequency oscillating current from the anode M to the resistance l9, butwhich impresses across the inductance 2l,-and consequently across the resistance l9 because of the high reactance of condenser l1 and the low reactance-pf condenser 20 at such frequency, the voltage on the anode M of the blocking frequency.

It is understood that the inductance 2| may be replaced by a'resistance, if desired, although an inductance is preferred to minimize power loss therein.- y

In a particular circuit in which thisarrangement was utilized to prevent blocking of the oscillations, the tuned circuits "land [6 and the device l2 were arranged to operate at frequencies above 3,000 megacycles. The resistance 19 was made 12,000 ohms, condenserZlJ was made 2,000 .micromicrofarads, and the inductance 2| was made l6 millihenries. Without the inductance 2| and condenser 20, blocking in the oscillating circuit was very severe, but when the inductance andcondenser were added was entirely eliminated. l

The arrangement for eliminating such blocking action may obviously be utilized in any form of oscillator subject to such action, suitable means being utilized in the oscillator to obtain an alternating voltage of the frequency of the blocking action, together with means for impressing this voltage on the resistance across which the bias potential for the control electrode is de veloped, such alternating voltage being impressed thereacross in such phase as substantially to,

pressing alternating voltage of the frequency f of an excessively large bias potentialacross the l An intermediate tap 33 on the inductance is connected through a condenser 34 to the cathode l5.

Discharge current is supplied to'the device 12 from a source 35 of operating potential therefor,

the negative terminal of the source 35 being' grounded. The current from the source 35 of potential flows through a circuit extending from thehpositive terminal of the source 35 through an inductance 33, intermediate tap 33 of inductance 30, the, upper portion of inductance 30, anode .14, cathode l5, and ground back to the electrode II is connected to ground and to the cathode l5 serially through a biasing resistance 31 and an inductance 38, which inductance is magnetically coupled with the inductance 36 as 1 explained hereinafter.

In operation the oscillator operates in usual fashion, the cathode l5 being maintained at an alternating potential intermediate the potentials of the control electrode II and anode M by its connection through the condenser 34 to the in termediate tap 33 on inductance 30. The osci1lations produced by the device l2 and the tuned circuits 30, 3 I are effective to cause current recti fication through the control electrode H and cathode 15 such that continuous current flows through the resistance 31. thereby developing a suitable biasing potential for control electrode ll.

In oscillators to which my invention may advantageously be applied, certain circumstances cause the operating bias developed across the resistance 31 to increase excessively, and to such values as to reduce the discharge current through the device l2 so much that oscillations produced ;by, the device l2 and the tuned circuits 30, 3!

v the discharge current through device I2 begins to decrease, causing a decrease in current flow through the inductance 36. This change in current flow through inductance 36 causes a corresponding potential to appear across the inductance 38, which is so poled as to cause the control electrode II to become less negative, or more positive, in potential. This action of the transformers .36, 38 in opposing excessive increases in bias potential produced across the resistance 31 is effective substantially to eliminate any blocking action of the oscillations produced by the device l2 and the tuned circuits 30, 3|.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. In combination, an oscillating circuit including an electron discharge device having, an anode, a cathode and a control electrode, means providing regenerative coupling between said anode and said control electrode to support oscillations, a resistance connected between said cathode and control electrode across which an operating bias potential for said control electrode is developed by reason of said oscillations,

a source of operating potential, a discharge current circuit for said device including said source,

I said anode and said cathode, said device having v a tendency to produce an excessive operating bias ing a current conductive impedance in said discharge current circuit between said source of 7 potential and said anode and a condenser connected from a point between said impedance and said anode to a point between said resistance and said control electrode.

2. In combination, an oscillating circuit comprising an electron discharge device having an anode, a cathod and a control electrode, means providing regenerative coupling between said cillations, and a resistance connected in circuit between said control electrode and cathode across which operating bias potential for said control electrode is developed by reason of said oscillations, a source of operating potential, a discharge current circuit including said source, said anode and said cathode, said discharge device having a tendency to produce an excessive operating bias potential on said resistance with consequent reduction of discharge current through said device thereby producing a recurrent blocking ofoscillations in said oscillating circuit and means qfor reducing such tendency comprising an inductance in said discharge current circuit between said source and said anode, and a con-,

, anode and said control electrode to support osdenser connected between a point between said inductance and anode and a pointbetween said resistance and control electrode, the reactance of said inductance being high and of said condenser being low at the frequency of blocking of said oscillations.

3. In combination, an oscillating circuit including an electron discharge device having an anode, a cathode and a control electrode, regenerative coupling between said anode and said control electrode to support oscillations, a resistance connected between said control electrode and cathode across which an operating bias potential for said control electrode is developed by reason of said oscillations, a source of operating potential, a discharge current circuit including said source, said anode and said cathode, said discharge device being effective to maintain oscillations in said oscillating circuit and having a tendency toward blocking such oscillations by developing an excessive bias potential on said resistance, the discharge current in saiddischarge device being simultaneously reduced, and means for reducing the tendency toward blocking such oscillations comprising a current conductive impedance in said discharge circuit between said source and said anode, means for preventing said oscillations from appearing across said impedance .and for producing a voltage across said impedance of the frequency of said blocking, and a'condenser connected from a point between said impedance and said anode to a point between said resistance and said control electrode for reducing said excessive operating bias potential on said control electrode in response to voltage on said impedance of the frequency of said blocking.

4. In combination, an oscillating circuit including an electron discharge device having an anode, a cathode and a control electrode, means providing regenerative coupling between said anode and said control electrode to support oscillations, a resistance connected between said control electrode and said cathode across which operating bias potential for said control electrode is developed by. reason of said oscillations, said discharge device having a tendency to produce an excessive negative bias potential across said resistance periodically to decrease the anode current of said device and to block said oscillations, and means responsive to said decrease of anode current for developing and supplying to said control electrode a potential opposed to said negative bias potential thereby to reduce said tendency'to block said oscillations.

WILLIAM W. MOE. 

